Electrically (Joule)-heated glass melters are used for the vitrification of nuclear waste. Due to the lack of on-line monitoring and capable measurement equipment, current processes rely on predictive models validated by more laboratory/melter testing with simulants but limited testing with actual radioactive wastes to predict and control the conversion process. Predictive modeling necessitates a more costly, conservative operation in order to take into account uncertainties in the process such as foaming, crystal formation, noble metals build-up, and salt layer formation. Additionally, predictive modeling will become more difficult in the future as waste glass chemistry evolves with changes in waste feed compositions and tank chemistries. Economical and environmental concerns thus dictate that improved methods of running this process be established.
Real-time measurements inside of a glass melter or other furnace are desirable in order to monitor performance of the furnace and to optimize the process. Presently, there are limited technological options. For example, infrared sensors may be employed in order to measure the temperature distribution within the furnace. Certain challenges exist, however, with such a measurement. The environment present within the furnace is often hot, smoky, and particle filled thus frustrating the ability of the infrared sensor to accurately measure temperature. Further, the temperature obtained from infrared sensors employed in furnaces may not be completely accurate since surface emissivity measurements are not acquired by the infrared sensors which are needed in order to accurately interpret temperatures. Additionally, as the black-body curve is non-linear in the IR region, sometimes two different emissivity values may be needed for certain ranges of temperature to measure it accurately.
Thermocouples can be used to obtain temperature inside of a furnace. However, the information obtained from these devices is limited to temperature data within the furnace and does not provide insight to other properties within the furnace for use in improving processing and performance. Further, the electrical wires associated with thermocouples have a limited heat/radiation tolerance and are prone to failure thus making their use in a furnace application less than ideal. Further, the thermocouple probe is not well suited for contacting certain materials to be measured, thus limiting their functionality in the furnace environment.
It is known to use a pyrometer with a single receiver in order to obtain temperature measurements within a furnace. Such known arrangements can employ a waveguide that is enclosed within a sleeve of alumina tubing. The end portion of the waveguide is located inside of the furnace and is easily replaceable in order to maintain performance due to its exposure to the harsh environment within the furnace. The waveguide is located away from material that is melted in the furnace, and the pyrometer is capable of obtaining limited information from the furnace such as temperature and emissivity, more often temperature, but not any other process parameters. Although capable of being used to obtain data from furnaces, the aforementioned arrangement is limited in the type of data that may be acquired for use in optimizing the measured process. Accordingly, there remains room for variation and improvement within the art.
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the invention.